This is already a decisive plan.
19. d2c4 A compromising move, since now Black can capture on f3 and weaken the pawn structure. The problem for White is that there's no active plan. If the knight on f4 is captured, then the g-file is opened, and the attack becomes very strong. 19... h5f3  20. g2f3  20... e7e6 Pinning the knight and also controlling the diagonal so that White cannot play Bf3 after capturing the f4-knight. 21. b3c2 Removing the pin.